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  <div class="section" id="construct">
<h1>construct<a class="headerlink" href="#construct" title="Permalink to this heading">¶</a></h1>
<div class="section" id="header">
<h2>Header<a class="headerlink" href="#header" title="Permalink to this heading">¶</a></h2>
<div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="cp">#include</span><span class="w"> </span><span class="cpf">&lt;boost/hof/construct.hpp&gt;</span><span class="cp"></span>
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description<a class="headerlink" href="#description" title="Permalink to this heading">¶</a></h2>
<p>The <code class="docutils literal notranslate"><span class="pre">construct</span></code> function returns a function object that will construct the
object when the called. A template can also be given, which it will deduce
the parameters to the template. The <code class="docutils literal notranslate"><span class="pre">construct_meta</span></code> can be used to
construct the object from a metafunction.</p>
</div>
<div class="section" id="synopsis">
<h2>Synopsis<a class="headerlink" href="#synopsis" title="Permalink to this heading">¶</a></h2>
<div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="c1">// Construct by decaying each value</span>
<span class="k">template</span><span class="o">&lt;</span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="o">&gt;</span><span class="w"></span>
<span class="k">constexpr</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">construct</span><span class="p">();</span><span class="w"></span>

<span class="k">template</span><span class="o">&lt;</span><span class="k">template</span><span class="o">&lt;</span><span class="k">class</span><span class="p">...</span><span class="o">&gt;</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">Template</span><span class="o">&gt;</span><span class="w"></span>
<span class="k">constexpr</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">construct</span><span class="p">();</span><span class="w"></span>

<span class="c1">// Construct by deducing lvalues by reference and rvalue reference by reference</span>
<span class="k">template</span><span class="o">&lt;</span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="o">&gt;</span><span class="w"></span>
<span class="k">constexpr</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">construct_forward</span><span class="p">();</span><span class="w"></span>

<span class="k">template</span><span class="o">&lt;</span><span class="k">template</span><span class="o">&lt;</span><span class="k">class</span><span class="p">...</span><span class="o">&gt;</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">Template</span><span class="o">&gt;</span><span class="w"></span>
<span class="k">constexpr</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">construct_forward</span><span class="p">();</span><span class="w"></span>

<span class="c1">// Construct by deducing lvalues by reference and rvalues by value.</span>
<span class="k">template</span><span class="o">&lt;</span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="o">&gt;</span><span class="w"></span>
<span class="k">constexpr</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">construct_basic</span><span class="p">();</span><span class="w"></span>

<span class="k">template</span><span class="o">&lt;</span><span class="k">template</span><span class="o">&lt;</span><span class="k">class</span><span class="p">...</span><span class="o">&gt;</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">Template</span><span class="o">&gt;</span><span class="w"></span>
<span class="k">constexpr</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">construct_basic</span><span class="p">();</span><span class="w"></span>

<span class="c1">// Construct by deducing the object from a metafunction</span>
<span class="k">template</span><span class="o">&lt;</span><span class="k">class</span><span class="w"> </span><span class="nc">MetafunctionClass</span><span class="o">&gt;</span><span class="w"></span>
<span class="k">constexpr</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">construct_meta</span><span class="p">();</span><span class="w"></span>

<span class="k">template</span><span class="o">&lt;</span><span class="k">template</span><span class="o">&lt;</span><span class="k">class</span><span class="p">...</span><span class="o">&gt;</span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">MetafunctionTemplate</span><span class="o">&gt;</span><span class="w"></span>
<span class="k">constexpr</span><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="n">construct_meta</span><span class="p">();</span><span class="w"></span>
</pre></div>
</div>
</div>
<div class="section" id="semantics">
<h2>Semantics<a class="headerlink" href="#semantics" title="Permalink to this heading">¶</a></h2>
<div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="n">assert</span><span class="p">(</span><span class="n">construct</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span><span class="p">()(</span><span class="n">xs</span><span class="p">...)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">T</span><span class="p">(</span><span class="n">xs</span><span class="p">...));</span><span class="w"></span>
<span class="n">assert</span><span class="p">(</span><span class="n">construct</span><span class="o">&lt;</span><span class="n">Template</span><span class="o">&gt;</span><span class="p">()(</span><span class="n">xs</span><span class="p">...)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">Template</span><span class="o">&lt;</span><span class="k">decltype</span><span class="p">(</span><span class="n">xs</span><span class="p">)...</span><span class="o">&gt;</span><span class="p">(</span><span class="n">xs</span><span class="p">...));</span><span class="w"></span>
<span class="n">assert</span><span class="p">(</span><span class="n">construct_meta</span><span class="o">&lt;</span><span class="n">MetafunctionClass</span><span class="o">&gt;</span><span class="p">()(</span><span class="n">xs</span><span class="p">...)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">MetafunctionClass</span><span class="o">::</span><span class="n">apply</span><span class="o">&lt;</span><span class="k">decltype</span><span class="p">(</span><span class="n">xs</span><span class="p">)...</span><span class="o">&gt;</span><span class="p">(</span><span class="n">xs</span><span class="p">...));</span><span class="w"></span>
<span class="n">assert</span><span class="p">(</span><span class="n">construct_meta</span><span class="o">&lt;</span><span class="n">MetafunctionTemplate</span><span class="o">&gt;</span><span class="p">()(</span><span class="n">xs</span><span class="p">...)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">MetafunctionTemplate</span><span class="o">&lt;</span><span class="k">decltype</span><span class="p">(</span><span class="n">xs</span><span class="p">)...</span><span class="o">&gt;::</span><span class="n">type</span><span class="p">(</span><span class="n">xs</span><span class="p">...));</span><span class="w"></span>
</pre></div>
</div>
</div>
<div class="section" id="requirements">
<h2>Requirements<a class="headerlink" href="#requirements" title="Permalink to this heading">¶</a></h2>
<p>MetafunctionClass must be a:</p>
<ul class="simple">
<li><p><a class="reference internal" href="../../../doc/src/concepts.html#metafunctionclass"><span class="std std-ref">MetafunctionClass</span></a></p></li>
</ul>
<p>MetafunctionTemplate&lt;Ts…&gt; must be a:</p>
<ul class="simple">
<li><p><a class="reference internal" href="../../../doc/src/concepts.html#metafunction"><span class="std std-ref">Metafunction</span></a></p></li>
</ul>
<p>T, Template&lt;Ts..&gt;, MetafunctionClass::apply&lt;Ts…&gt;, and
MetafunctionTemplate&lt;Ts…&gt;::type must be:</p>
<ul class="simple">
<li><p>MoveConstructible</p></li>
</ul>
</div>
<div class="section" id="example">
<h2>Example<a class="headerlink" href="#example" title="Permalink to this heading">¶</a></h2>
<div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="cp">#include</span><span class="w"> </span><span class="cpf">&lt;boost/hof.hpp&gt;</span><span class="cp"></span>
<span class="cp">#include</span><span class="w"> </span><span class="cpf">&lt;cassert&gt;</span><span class="cp"></span>
<span class="cp">#include</span><span class="w"> </span><span class="cpf">&lt;vector&gt;</span><span class="cp"></span>

<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
<span class="w">    </span><span class="k">auto</span><span class="w"> </span><span class="n">v</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">boost</span><span class="o">::</span><span class="n">hof</span><span class="o">::</span><span class="n">construct</span><span class="o">&lt;</span><span class="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o">&lt;</span><span class="kt">int</span><span class="o">&gt;&gt;</span><span class="p">()(</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p">);</span><span class="w"></span>
<span class="w">    </span><span class="n">assert</span><span class="p">(</span><span class="n">v</span><span class="p">.</span><span class="n">size</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">5</span><span class="p">);</span><span class="w"></span>
<span class="p">}</span><span class="w"></span>
</pre></div>
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